Category "recursion"

Map of sets into list of all combinations

I'm stuck with a simple task. What I want to do is to transform Map<K,Set<V>> into the List<Map<K,V>> getting all possible combinations:

If myStr = 'test', why does myStr[4] produce error out of range but myStr[4:] does not?

I'm using recursion to iterate through the values of a string. When I get past the last character, it's allowing me to use that index position as an empty strin

Why is there no tail recursion optimization in Emacs lisp, not but like other scheme?

Emacs lisp is a dialect of LISP and especially Scheme. Most of scheme interpreters do have a optimization of Tail Recursion, but emacs lisp doens't. I searched

Lazy Catalan Numbers in Haskell

How might I go about efficiently generating an infinite list of Catalan numbers? What I have now works reasonably quickly, but it seems to me that there should

recursive tree as a list (array items) in a new attribute value child

How to get hierarchy data(recursive tree) as a new column like below? (if there is last child then column child array is empty) rows: [{ 'id' : 1, 'paren